1. Field of the Invention
This invention generally relates to methods for stereoscopic imaging and, more specifically, to a device that acquires stereoscopic images.
2. Description of Related Art
The use of stereoscopy, in which the user sees left- and right-eye views and forms a three dimensional image through stereopsis, is common in many areas of science, medicine and entertainment. The use of a binocular to provide a magnified stereoscopic image of distant objects to a user's eyes is also common. Binoculars are used for observation, surveillance, and many other purposes.
The optical image generated by a binocular is typically viewed through eyepieces. However, the use of eyepieces in binocular systems is often problematic. Furthermore, only one observer at a time can view images generated by the binocular and the observer can no longer see what is happening in the surrounding environment. In addition, a binocular, as such, cannot store images or sequences of images for later playback, process them in special ways, or transmit them to remote viewing sites. There are also situations in which it is desirable to remotely view or record a stereoscopic image of a location without involving a person to take the image.
Therefore, it is often desirable to use electronic imaging to acquire images of a location, either for direct, real-time observing or for recording Electronic imaging is a preferred method of the television broadcasting, video and movie industries as well. The use of cameras and electronic displays to acquire images is well known in the art, including the use of two cameras and a 3D display to give a stereoscopic image.
However the two-camera systems have many disadvantages. Obtaining and maintaining stereoscopic alignment (necessary for comfortable, long-term viewing) can be very difficult when two independent cameras are mounted on or comprise a binocular. The cameras generally protrude from the general body of the device and are often mounted in a way that is fragile and prone to breakage. Protruding cameras can interfere with other apparatuses in the workspace, limiting possible usage configurations. The two-camera systems have generally double the binocular and camera knobs and controls, resulting in an unwieldy device difficult to operate by a single user. Dual camera systems generally require numerous mounting parts, resulting in less reliability and more cost than a single, integrated camera.
There are also problems with mounting and connecting the cameras to displays or storage media. The use of two cameras requires multiple cables and connectors, resulting in less reliability and more difficult installation than a single cable/connector arrangement of the present invention. The two-camera system also typically requires two camera control units (CCUs) and two storage devices, and requires that they be synchronized for best image quality. This significantly increases the cost of the system.
In addition, such cameras do not allow precise positioning of the imaging sensors to each other for best stereopsis and comfortable viewing, particularly when two off-the-shelf cameras are used. Cameras which are wide cannot be easily positioned side-by-side with close spacing. The cameras must be individually focused after mounting, and, should adjustments such as brightness and contrast be needed, each camera must be controlled individually. Where the cameras contain irises, they must also be individually adjusted for each camera, resulting in the potential for unequal amounts of light entering each camera, which can lead to difficult 3D viewing and eyestrain. All these factors indicate that using such a system requires skill and can be very time-consuming.
Image processing is also problematic in such systems. The cameras must be electronically linked in some way so that the two image streams are synchronized, creating additional cost and complexity. Even if the data streams are synchronized, generally the shutters are not perfectly synchronized such that the nth pixel from one view was not captured at the same time as the nth pixel from the other view, causing moving objects to show spurious parallax when displayed. Furthermore, the images acquired by the two cameras are generally taken directly to the 3D display device. Therefore, should the user require image processing, storage, transmission, or display on alternative displays, additional processing units are required, creating additional cost and complexity.
The cameras used in such two-camera systems also usually conform to the NTSC or PAL video standard, both of which suffer from low resolution, poor color fidelity, and motion artifacts (due to the interlaced nature of the raster scan). Recording and editing recorded content is also problematic with the two-camera system. Recorders don't generally start and end synchronously, so the two tapes or files must somehow be synchronized, resulting in additional effort and expense. Editing may need to be performed twice—once to each file or tape.
Information relevant to attempts to address these problems can be found in U.S. Pat. Nos. 4,418,993; 4,583,117; 4,879,596; 4,881,122; 5,164,827; 5,438,386; 6,157,337, and 6,512,892.
However, each one of these references suffers from one or more of the following disadvantages: the device or system creates two independent output signals; is not compact; does not provide sufficient image processing, recording, or transmission capability; does not have adequate resolution in real-time for many applications; is cumbersome or is not easily operated by a single user; is large and expensive; more than one operator is generally needed to properly control all of the required functions in order to provide good images,; it is difficult to synchronize two separate cameras to the pixel level; two recording devices or image-capturing paths are required, resulting in additional complexity and cost in acquiring and recording the images and editing them as is often desirable; accessory image/data recording systems have a required start-up time prior to recording; uses significant power, requiring large batteries for mobile applications and emitting significant heat that could disturb sensitive environments; is more fragile than a single camera; or does not perform well if either or both of the cameras uses automatic focusing, automatic exposure control or image stabilization control, because such systems or devices heretofore have not been synchronized for the two views from the two cameras;
Therefore, the use of binocular systems containing electronic cameras, recording devices and display therefore solves some of the eyepiece problems but creates new ones, essentially making them impractical for routine use.